1. Field of the Invention
The present invention relates to a method and apparatus for measuring geometry elements, which calculates geometry elements to be measured, on the basis of measured data obtained from a measuring machine such as a three-dimensional coordinate measuring machine and a form measuring instrument, and outputs them as measured results.
2. Description of the Related Art
A three-dimensional coordinate measuring machine is employed to measure geometry elements of works to be measured, such as points, lines, planes, circles, spheres, cylinders and cones. The machine first indicates a geometry element to be measured from a console then measures significant number of points required for measuring the geometrical form. For example, if the geometry element is a point, a probe is brought into touch with a position to be measured to obtain measured data from one point. If the geometry element is a plane, it is required to obtain measured data from at least three points on that plane. Then, some computational operations are executed to derive the indicated geometry element from one or more measured data.
In such the method of measuring, however, an operation for indication of geometry element is required during an interval between measurement operations by the probe directly or using a joystick, resulting in a lowered operability and causing a measurement error. JP 8-82521A proposes another method of measuring geometry elements, which omits the indication of geometry element to improve the operability. This method receives measured data of a work to be measured and applies the measured data in arithmetic expressions for respective geometry forms previously stored. It compares formal errors obtained from the arithmetic expressions and determines a geometry form with the minimum formal error as the geometry element to be measured.
The present invention has a first object to provide a method and apparatus for measuring geometry elements, which can reduce the computational complexity of data in the above-mentioned conventional method of measuring geometry elements to perform a high-speed processing.
The present invention also has a second object to provide a method and apparatus for measuring geometry elements, which can further improve the operability in the above-mentioned conventional method of measuring geometry elements.
The present invention is provided with a first apparatus for measuring geometry elements, which comprises: a measuring machine for measuring one or more sample points on a work required to calculate a geometry element which defines the work to be measured and outputting measured data; a sampling and sample processing section for receiving the measured data of the sample points measured by the measuring machine and counting the number of the sample points received; and an element discriminating section for discriminating the geometry element which defines the work to be measured on the basis of the number of the sample points received by the sampling and sample processing section and a distribution of all sample points.
The present invention is also provided with a second apparatus for measuring geometry elements, which comprises: a measuring machine for measuring one or more sample points on a work required to calculate a geometry element which defines the work to be measured and outputting measured data; a sampling and sample processing section for receiving the measured data of the sample points measured by the measuring machine and counting the number of the sample points received, the sampling and sample processing section determining the finish of reception of all sample points required to calculate the geometry element when a predetermined time is elapsed after the last measured data is received; and an element discriminating section for discriminating the geometry element which defines the work to be measured on the basis of the measured data and the number of the sample points received by the sampling and sample processing section.
The present invention is further provided with a first method of measuring geometry elements, which comprises the steps of: receiving one or more sample points on a work required to calculate a geometry element which defines the work to be measured and counting the number of the sample points received; determining a distribution of the sample points received in the step of receiving; and discriminating the geometry element to be measured on the basis of the distribution of all sample points determined in the step of determining and the number of the sample points counted in the step of receiving.
The present invention is still further provided with a second method of measuring geometry elements, which comprises the steps of: receiving one or more sample points on a work required to calculate a geometry element which defines the work to be measured and counting the number of the sample points received; determining the finish of reception of all sample points required to calculate the geometry element when a predetermined time is elapsed after the last sample point is received in the step of receiving; and discriminating the geometry element to be measured on the basis of the measured data and the number of the sample points after the finish of reception of all sample points is determined in the step of determining.
According to the first method and apparatus for measuring geometry elements of the present invention, it determines a distribution of one or more sample points on a work required to calculate a geometry element which defines the work to be measured. On the basis of the distribution and the number of the sample points, it discriminates the geometry element to be measured. Therefore, it can determine the geometry element with much lesser computational complex than that of the conventional method, which performs application processes of all geometry forms and their error calculations based on measured data, thereby greatly reducing the computational complexity of data to achieve a high-speed processing.
The measuring machine may comprise a three-dimensional coordinate measuring machine for outputting measured data that contains three-dimensional coordinates. In this case, the distribution of the sample points can be determined as any one of zero through third degrees on the basis of a thickness, width and height of the minimum rectangular parallelepiped that internally contains all sample points received.
The element discriminating process may be performed to discriminate the geometry element as: a point when the number of the sample point is equal to 1; a line when the number of the sample points is equal to 2 or more and the distribution of the sample points is of the first degree; a plane or a circle when the number of the sample points is 2 or more and the distribution of the sample points is of the second degree; a sphere when the number of the sample points is equal to 4 or 5 and the distribution of the sample points is of the third degree; and a cylinder or a circular cone when the number of the sample points is equal to 6 or more and the distribution of the sample points is of the third degree.
When the number of the sample points is equal to 2 or more and the distribution of the sample points is of the second degree, the geometry element can be discriminated as: a plane if the approaching direction for measurement which is employed when at least the last sample point is obtained (for example, the moving direction of the probe toward the position to be measured) is vertically close to a plane defined by the sample points; and a circle if the approaching direction for measurement is parallel close to a plane defined by the sample points.
When the number of the sample points is equal to 6 or more and the distribution of the sample points is of the third degree, calculation of a half vertical angle of circular cone from the measured data allows it to discriminate the geometry element as: a cylinder if the half vertical angle is equal to or less than a predetermined value; and a circular cone if the half vertical angle is larger than the predetermined value.
According to the second method and apparatus for measuring geometry elements of the present invention, during receiving one or more sample points on a work required to calculate a geometry element which defines the work on a work to be measured, it determines the finish of reception of all sample points required to calculate the geometry element when a predetermined time is elapsed after the last sample point is received. Therefore, an operator is not required to operate to indicate that measurement of required sample points is finished and he/she can concentrate all measuring operations on accessing to measuring positions by the probe to improve the measuring operability.
Other features and advantages of the invention will be apparent from the following description of the preferred embodiments thereof.